Toxoplasmosis. An experiment is in progress to determine if reactivation of toxoplasmosis in immunocompromised hosts is due to proliferation of "cryptic" endozoites or cyst rupture or both. Studies show that trimetrexate combined with sulfadiazine in the treatment of toxoplasmosis may be a safe and effective alternative to pyrimethamine and sulfadiazine in the treatment of toxoplasmosis. Circulating antigen has been found in sheep infected with toxoplasmosis beginning 2 weeks post infection. Antigen has also been found in the aborted fetuses from acutely infected sheep. Schistosomiasis. ELISA for the detection of circulating antigen (GASP) reported last year is still being evaluated. Sera are currently being examined from S. japonicum patients from NAMRU 2 in the Philippines.